The present invention relates to a method for the production of heat and/or fluid exchangers containing tubes through injection molding of a thermoplastic material by means of an injection mold comprising at least two parts, such as a top mold and a bottom mold. The present invention also relates to an apparatus for the production of heat and/or fluid exchangers containing tubes through an injection mold comprising at least two parts for the implementation of said method.
A method and an apparatus for the production of fluid exchangers has been disclosed in German Patent Application No. 28 24 934 in which a bundle of hollow filaments is inserted into a casting mold which is then filled with molten thermoplastic material. After the thermoplastic material has solidified, the bundle of filaments is removed from the mold and cut within the range of the solidified thermoplastic material. In this manner, two tube bases are created. If tube bases are molded onto both ends of the bundle of hollow filaments, a fluid exchanger is created which then needs to be fitted with the required connections and which may be placed inside a housing. German Patent Application No. 28 24 934 further discloses that attempts had already been made to obtain tube bases by pressure impregnating each end of the precut bundle of hollow filaments with polymeric materials. This pressure impregnation presents a drawback, however, in that the extremely thin walls of the hollow filaments would break or be crushed and that the open ends of the filaments easily clog up.
German Patent Application No. 30 27 087 discloses a generic method in which several tubes are provided with a tube base by injection molding, with projections being inserted into the tubes for purposes of injection molding. However, this method can only be applied when, after injection molding, the tubes are in one plane. The strength of the bond between the tubes and the tube base barely exceeds the strength achieved by adhesive bonding. This method becomes very costly when, after injection molding, the tubes are to be positioned in several planes. Frequently, this method cannot be used at all because of the positioning desired for the tubes.
It is also known from European Patent Application EP-A-22 234 to bond metal tubes with a tube base by first inserting the metal tubes into the tube base and then coating the outside of the tube base with adhesive material. To enhance the strength of the adhesive, the latter may be subjected to increased pressure after the coating. In addition, the metal tubes are connected between the two tube bases by a plurality of lamellae. This type of bonding demands many steps in the production, and the curing of the adhesive bond takes a long time. The coating of the tube base with adhesive also takes a long time and requires increasing care as the number of tubes to be glued to the tube base is raised.